This invention relates to a fluid flow diverter valve with an improved flow-through construction.
It has previously been suggested that heat exchanger tubing may be internally cleaned by mounting brush-basket assemblies on the ends of the tubes, and then by flowing fluid first in one direction and then the other to cause the brushes to traverse the length of the tubes and then return to their original position. See the above-identified U.S. Pat. No. 3,319,710.
It has also previously been suggested as in the above U.S. Pat. No. 3,973,592 to utilize a fourway diverter valve for purposes of reversing fluid flow within the tubes to cause the cleaning brushes to move in both directions within the tubes. In diverter valves of the '592 type a butterfly valve element having head members joined by a central plug is rotatable between normal and reverse flow positions. Four cage bars are circumferentially spaced and form pairs of opposed seats for sealing engagement with the two edges of the valve plug to connect various chambers within the valve housing with upstream and downstream fluid flow lines, depending on the rotary position of the valve element.
Valves of the of the type shown in U.S. Pat. No. 3,973,592 are subject to several disadvantages. The use of four cage bars for plug sealing, and the utilization of numerous walls and partitions within the valve housing, creates a complex structure which is expensive to manufacture and service. Furthermore, some of the fluid flow paths through the valve housing are quite tortuous, resulting in high pressure drop which is especially undesirable in the more frequently used normal flow position. In some instances, the fluid is caused to make as much as a complete 360.degree. turn within the valve.
A more recently developed diverter valve has been thought to solve some of the problems of the above-described type of valve. The more recently developed valve, sometimes called a "pipe" valve, is disclosed in my co-pending U.S. patent application Ser. No. 06/475,203, filed Mar. 14, 1983 and entitled "Four-Way Fluid Flow Diverter Valve", now U.S. Pat. No. 4,506,703, issued Mar. 26, 1985. In the pipe valve of my aforesaid application, a cylindrical housing is provided with the usual pairs of in-line upstream and downstream ports, and contains a tubular diverter having a central diametrical baffle which forms separate but parallel fluid flow passages therein. The tubular diverter is rotatable between normal and reverse flow positions, and the diverter length approximates the diameter of the cylindrical housing. The diverter ends are constructed to sealingly seat on concave seat members forming part of the valve body and disposed adjacent a pair of diagonally opposed valve ports. In addition, the tubular diverter is provided on its exterior with diametrically opposed longitudinally extending radial ribs which are adapted to engage stop members which in turn are disposed on the end closure plates for the cylindrical wall of the housing. The engagment of the tubular diverter ends with the cylindrical valve body seats, and the engagement of the said ribs with the said stop members are intended to substantially reduce by-passing of fluid between the supply or high pressure side and the return or low pressure side of the valve, especially when the diverter is in normal position. The tubular diverter may be adjusted along its rotary axis for controlling and preferably reducing the said fluid flow by-passing.
The pipe valve of the type described above is much more simply constructed than the valve of U.S. Pat. No. 3,973,592 and is thus less expensive to manufacture and maintain. Furthermore, when the tubular diverter element is in its most frequently used normal position, supply and return fluid flows are almost in a straight line through the valve chamber and diverter, thus reducing undesirable pressure drop to a minimum.
It has been discovered that while the above-described pipe valve has substantially solved the problems of complexity, cost and pressure drop, it is subject to other disadvantages.
Under high pressure conditions, it has been observed that the fluid flowing through the pipe valve may under certain conditions cause distortion of the cylindrical valve housing. In such a situation, the housing becomes out of round and the seals between the tubular diverter ends and the concave valve housing seats no longer are in full contact and are effectively broken, thus permitting undesirable leakage from the high to the low pressure side. Distortion of the said stop members may also cause by-passing leakage along the diverter sides. While such leakage may be tolerated when the tubular diverter is in its short-term reverse position, it is undesirable in the long-term normal position. The distortion-caused leakage may under some circumstances be substantially reduced at the tubular diverter ends by a tightening adjustment of the diverter along its axis. However, such adjustment will not reduce leakage between the radial ribs and stop members.
A reduction of the distortion and leakage problems in the aforementioned pipe valve may be provided by manufacturing the valve housing of substantially stronger non-deformable material and by machining the contacting sealing surfaces to much closer tolerances. However, such procedures are costly and may make the value uneconomic from a commercial standpoint.
It is a task of the present invention to reduce the complexity of four-way valves such as of the type disclosed in U.S. Pat No. 3,973,592 by providing a "pipe" valve of less complexity and wherein pressure drop in normal position is substantially reduced by providing straight-through fluid flow.
It is a further task of the present invention to reduce the difficulties discovered with the pipe valve of my aforesaid application so that possible distortion of the valve housing will not effectively reduce the sealing efficiency thereof, either at the ends of the tubular diverter or between the diverter and the end closure plates for the cylindrical housing walls.
It is yet another task of the invention to permit tightening adjustment of all the seals within the valve housing. It is a further task to accomplish all of the above tasks in an economical manner.
In accordance with the various aspects of the invention, a four-way diverter valve is constructed with a rotatable butterfly valve element within the cylindrical valve housing and with said element having a pair of end heads joined by a generally planular central tapered plug of longitudinal extent. The valve plug is modified by having mounted thereon between its ends a tubular diverter means which comprises a pair of transversely extending pipe segments, one mounted on each side of the plug, which forms a baffle. The segments are formed of a piece of circular tubing which is cut down the middle and with the exposed edges cut back a total of the plug thickness. Additionally, the pipe segments are of substantially less length than the diameter of the valve housing and terminate adjacent the plug edges.
The valve housing is connected to two pair of in-line ports and stub pipes are fixedly mounted to the housing wall, communicate with a pair of diagonally opposed ports, and extend inwardly from the housing wall toward the modified butterfly valve element and the tubular diverter means. The diverter pipe segment ends are free of the housing wall at all times. In normal valve position, a generally straight-through fluid flow is provided. In reverse valve position, the ends of the diverter pipe segments engage the ends of the stub pipes to provide a diagonally reverse fluid flow channel.
Only two opposed cage bars are utilized with the butterfly plug edges sealing against the cage bars for substantially the full axial extent of the cylindrical housing, in normal valve position. The butterfly valve heads also seal against annular sealing surfaces on the housing. Simultaneously controllable sealing is accomplished both within and without the tubular diverter means.